1. Field of the Invention
The present invention relates to an apparatus and method for transmitting/receiving a signal in a signal transmission/reception apparatus of a communication system. More particularly, the present invention relates to an apparatus and method for transmitting/receiving a signal after removing an echo signal in a signal transmission/reception apparatus of a communication system.
2. Description of the Related Art
In a conventional communication system, a signal is transmitted/received through a direct link between a Base Station (BS) and a Mobile Station (MS). More specifically, a BS provides service to the MS when the MS is in the service coverage area of the BS. However, in the conventional communication system, a location of the BS is fixed. Accordingly, it is difficult to supply an effective communication service when the MS enters a shadow region in the service coverage area or when there is severe variation of a channel state. In the conventional communication system, one method of addressing this problem is to install a Relay Station (RS). A Relay Station (RS) is provided between the BS and the MS and is used for amplifying the BS signal and therefore extends the service coverage area of the BS.
The conventional communication system can extend a cell service area and provide a channel with an improved channel state to an MS using the RS. Further, the BS can provide a faster data channel to an MS using the RS in a cell boundary region having a degraded channel state.
FIG. 1 is a diagram illustrating a structure of a conventional communication system using an RS.
Referring to FIG. 1, the conventional communication system includes a BS 110, an RS 130, and an MS 150.
The BS 110 can transmit a data signal to the MS 150 either directly or using the RS 130. Similarly, the MS 150 can transmit a data signal to the BS 110 either directly or using the RS 130.
The RS 130 amplifies a signal received from the BS 110, and transmits the amplified signal to the MS 150. The RS 130 also amplifies a signal received from the MS 110, and transmits the amplified signal to the BS 150. Further, the RS 130 includes at least one antenna for transmitting/receiving a signal.
In FIG. 1, it will be assumed that the RS 130 includes two antennas, i.e., a transmission antenna for transmitting a signal and a reception antenna for receiving a signal.
When the RS 130 transmits a signal, the signal transmitted through the transmission antenna can be received through the reception antenna. That is, the signal transmitted through the transmission antenna can flow into the RS 130 along with a signal received through the reception antenna. If the signal transmitted through the transmission antenna flows into the RS 130 along with the signal received through the reception antenna, the signal transmitted through the transmission antenna that flows into the reception antenna will be called an “echo signal”.
When the echo signal is received, it causes oscillation in the RS 130. Also, the intended signal received through the reception antenna is distorted due to receipt of the echo signal in the RS 130. Accordingly, when the signal received through the reception antenna is distorted, the quality of a signal transmitted by the RS 130 is decreased.
Therefore, there is a need for a signal transmission/ reception apparatus that removes an echo signal in order to prevent the quality of a transmission signal from decreasing due to an echo signal in the conventional communication system.